Typewriting machine



Sept. 5, 1939. A boBS N 2,171,688

TYPEWRITING MACHINE Filed Dec. 10, 1936 47 Illi i ATTORNEY.

Patented Sept. 5, 1939 UNITED. STATES PATENT OFFICE TYPEWRITIN G MACHINE Application December 10, 1936, Serial No. 115,095

4 Claims.

This invention relates to stop-devices employed in typewriter case-shift mechanisms.

Certain stop-devices heretofore used include noise-reducing cushioning means such as leather,

4 felt, rubber, cork, or the like, which, being yielding and soft, do not stand up or wear well and therefore these devices are not effective to maintain the requisite accuracy of movement to which the case-shift parts must be limited by the stopdevices. a

The conventional solid metal abutments heretofore used are too noisy.

A feature of my invention is the provision of an inexpensive stop-abutment capable of arresting a 157? case-shift mechanism with accuracy, and so quietly as to be comparable with the old cushioned abutments.

I obtain the result by constructing an abutment of a wide' fiexib-le button formed of steel or other 20 hard material possessing only slight yieldability. The steel button, after being formed, is left soft. A central concavity may be formed in the top, so that therim may yield slightly under impact, to absorb the noise-producing vibration. The rim is 25 not so yieldable but that a precise and accurate arresting stop is provided and, when the device is applied to a typewriter case-shift, accurate aligning of the platen is procured.

The arresting button may be centrally mounted 30.1 on top of an adjusting screw which may also support a locking nut, so that the arresting position of the stop may be varied and set. A good quality steel assures both a good decibel standard and permanence of precision.

35 The bottom of the concave recess may provide a positive stop against excessive bending of the rim of the arresting device. The recess should be preferably shallow and broad so that the center a and bottom of the cavity, which is positioned di- 40" rectly" over the mounting and adjusting screw, when intercepted by the moving or striking part, provides a positive check against excessive yielding of the rim downward.

Another feature of the invention is the pro- 45 Vision of a novel device for locking the caseshifting mechanism in lower-case position, to prevent platen rebound and thereby to assure a perfect alignment of the line of typing. The end of the shift-key lever may be provided with a de- 50 pending tooth which overlies the upper rear edge of an upwardly extending finger which is fixed on one of the case-shift lift arms; the tooth is raised to clear the finger before the shift-key lever raises the lift arm and the lift arm moves the 5.5 finger into locking position before the return spring on the shift-key lever lowers the depending tooth-into locking position. The bottom of the tooth may be rounded to facilitate the movement into locking position. The locking tooth may be mounted for forward and backward adjustment 5 on the end of the shift-key lever.

Other features and advantages will hereinafter appear.

In the accompanying drawing:

Figure 1 is a top-front view at an angle of 45, 10 with a part of the silencer stop broken out.

Figure 2 is a side elevation of the inside of the frame showing two opposed stops and the caseshift lift arm in upper-case typing position.

Figure 3 is a side elevation showing an adjustable lock for locking the case-shift in lower-case position.

Figure 4 is a side elevation partly sectioned to show the contacting relationship of the extension on the case-shift lift arm and the silencing stop.

Figure 5 is a view similar to Figure 4 but showing an exaggerated and magnified bending of the silencing stop.

Figure 6 is a view similar to Figure 4 but showing a further exaggerated and magnified bending of the silencing stop to the final limit in which the engagement of the extension on the case-shift lift arm and the bottom of the top cavity on the silencing stop takes place.

A typewriter frame I0 is mounted on the usual legs I I. A shift-key lever I2 is pivoted on a crossrod I3 mounted in the frame ID. A stop-pin I 4 in the side of the frame II] determines the initial position of the shift-key lever and a coil spring I5 is fastened to the shift-key lever on the opposite side of the pivot-rod I3 and to the frame I0 and thereby tends to return the shift-key lever I 2 to the initial upper position.

A downwardly and rearwardly inclined arm I6 has a top level operating edge I I, the latter engaging a transverse pin 48 mounted on a caseshift lift arm I9 which is mounted on a rock-shaft 20 for reciprocation therewith, the shaft being journaled in the sides of the frame It]. The pin I8 engages an aperture in the shift-frame 22 to actuate the latter in case-shift movement. Also mounted on the rock-shaft 20 is an upstanding finger 2 I. In the normal idle position of the shiftkey lever I2 and the lower-case position of the 50 case-shift lift lever I9 the pin I8 lies a bit above the operating edge I'I, thereby permitting upward motion of the rear of the shift-key lever before the edge I! engages and actuates the pin I8 to raise the lift arm I9 and the shift-frame 22 of the upper stop 4|.

which is mounted to slide upwards and downwards in the frame III by a pin-and-slot connection 23, as is well known in the art. The shiftframe 22 supports tracks 24, 25 which together with tracks 26, 21, mounted on the platen-carriage 29, engage anti-friction balls 28. A rotatably mounted platen 30 is engageable by a typebar 3! in a manner well-known in the art. The depression of the shift-key elevates the platen to the upper-case type position 32.

The case-shift lift arm l9 has an extension 33 which projects forwardly in substantially a hori zontal direction to lie between parallel-horizontalears 34, 35 mounted on the inside of the side wall of frame l0 and projecting-inwardly. The ears 34, 35 have holes centered on aperpendicular line which are internally threaded to receive identical screws or studs 36, each of which has inits end a slot 31 to secure a screw-driver. The screw 36 is not threaded near the top, to leave a section 38" which acts as a stop and spacer-fora nut 39, the latter forming a massive: body portion on the stud 36 and having the usual hexagonal periphery:

to receive-an adjusting wrench- Lock -nuts.4|l engage .theears .34 to lock-the screws 36 in any ad-' justed position.

Each screw-'36 supports on its .top, a relatively thin arresting stop or diaphragm 4| centrally positioned thereon. This stop..4| may bespaced from the top of nut 39 by-thelength of the section 38 and may-have a flat bottom and on the top is dishedto forma circular shallow centrally positioned concavity-46 which .forms a vfiattopped rim.41, the periphery ofwhich may be of identical-polygonaLform withthat of the body portion. 39.. The-cavity 46' is preferably broad and shallow, in fact sufficiently shallow to permit the rim 41 to flex downwardly on. opposite sides at the same. time asoshown exaggerated in Figure 6 so that the bottom 48-.ofthe concavity forms a positive final stop for the lower straight edge 49'of extension. 33 in thecase of the lower stop -4|, .and.for.- the. angularly disposed. upper straight edge 50 of the extension 33-,in the case This prevents fatiguing and preventsbreakdown-ofthe diaphragm 4|. The steel of thearresting stop-button 4| is pref.- erablyleft soft to givethe desired-flexibility and silencing property, and. When-the silencer stop 4| is tested on a decibel machine, theresult compares favorably. with cushioning stops that are utterly lacking in the accuracy of. alignment. of the platen and the actuatinglongevity inherent in the present: invention. The body portion 39 may alsoserve to choke some of the noise-producing vibrations set up. in. the screw 36.

The shift-keylever l2 terminates in a rearward.

arm. 52-.having near the rear endacentral elongated slot 53. A piece 54 carries-at the: outer end;

a depending; tooth 55, theiront edge of which is adapted to engagethe upper rearstraight edge of the finger 2|. The piece 54 has bent-over tabs 56 which slidably engage opposite edges of the arm 52. A set screw 51 passes through the slot 53 and is centrally secured on the piece 54, the

overlying head of the screw pressing on the near side of the arm 52, as shown in Figure 3.

The play between the inclined edge H of the arm l6 and the pin l8 permits the tooth to rise high enough to clear the top of the finger 2| Whenthe shift-key is depressed, and also permits the finger 2| to fall into the initial position. The tooth 55 may be appropriately curved at the bottom.-to..-permit sliding engagement into the engaging position over the top of the finger 2|.

Variations may be resorted to within the scope of the invention, and portions of the improvements may be used without others.

Having thus described my invention, I claim:

1. In a case-shift mechanism for typewriters, a silencing stop engageable by a member of the mechanism for limiting relative movement of the platen to the type, and comprising, a mounting stud;. anda flexible metallic diaphragm carried on the'end .ofsaid stud andadapted to flex laterallyupon engagement with said member.

2. In a case-shift mechanism for typewriters, a. silencing stopengageable by a -member of the mechanism for limiting relative movement of the platen-to the type, and-comprising, a. mounting stud, and a flexible metallic diaphragm carried on the end of said stud and presenting a vsubstantially broad area to the path of saidmember, a-medial-portion of'the area being concave to present alimitedmarginal area for engagement with said member. I

3. In a case-shift mechanism for typewriters, a silencing stop engageable bya member of the mechanism for. limiting relative. movement of the platento. the type, and comprising, a slim mounting. stud; a.flexible, thin metallic button carriedon the end of-said-stem,.presentinga substantiallybroad area to said member and adapted to flexlaterally upon engagement with said member, and amassive body portion-on said stem. adjacent but spaced from said button to dampenimpact vibrations imparted to said stop.

4. In a case-shift mechanism. for typewriters, a silencing stop engageable by a member' of the mechanismforalimiting relative movement of the platen to the type, andcomprising, amounting stud; anda flexible, thin metallic diaphragm having a. shallow concavity in the facethereof confronting saidmember and presentinga marginal area only for initial engagement by saidmember, said.diaphragm.-beingadaptedto flex upon engagement bysaid memberto the extent of the depth oftheconcavity, the extent of fiexure being limited by said member engagingthe bottom of the concavity.

WILLIAM A. DOBSON. 

